Use daylight
Daylight near a window beats any lamp. Turn the ceiling light off, stay out of harsh midday sun, and the colours will look the way they do in real life.
A plain background
A plain wall, a clear floor or a smooth bedspread lets the piece stand out. Hang it, lay it flat or wear it: whichever shows the shape best.
The cover photo
Your first photo is the cover in the shop. Show the whole piece, straight on, filling most of the frame.
Then the details
Add close-ups of the fabric, the buttons, the zip and any print, and snap the size and care labels. If there’s a mark, a pull or a missing button, photograph that too: showing it now saves an awkward message after the sale.